Accessories
Screen
YBR125, Yamaha make a small screen for the bike.
But you can get a much bigger and better (and make bike go faster) screen, google Givi A660 screen review to find my review.
CBF125, the original screen is more cosmetic than practical since it's so low.
Givi and Honda make much taller screens for the CBF125,
If I had a CBF125 I would buy one of them, since it speeds bike up, reduces wind fatigue and fuel consumption.
CBR125, I bet there are aftermarket companies that make taller screens.
If the original screen does not protect the top of your body from the wind, you need a taller screen.
Fork Gaiters
See Fork Gaiters
Luggage
Givi and Honda make Honda CBF125 rear racks.
Givi make a Honda CBR125 rear rack.
I have not fitted a rear (luggage) rack, since I have always found on any bike,
that carrying weight behind the back wheel messes up the bikes cornering abilities,
catches the wind (if there is a back box) and cannot carry a lot of weight without making the bike un controllable.
I have found the best place to carry weight is the passenger seat.
You can carry as much weight as you like, it does not catch the wind since your body is sheltering it.
It very slightly effects the cornering ability of the bike with heavy items
(you will probably not even notice unless you excessively lean the bike).
The downside of using the passenger seat is it's much harder to get on and off the bike
(use a pavement curb if your legs are not up to it).
Uphill is much easier to get on and off compared to downhill, using the side stand does help.
You can buy a motorcycle seat bag, or just tie your item down with the luggage strap supports on the bike.
If using the passenger seat is not an option, try a tank bag or panniers (catches the wind).
You can stop the straps from rubbing the paint off the bike, by putting stickers or other plastic sticky material on the paintwork.
You may be able to find transparent plastic film that is designed to protect paint,
it can often be removed with a hairdryer and residual adhesive with paint thinner or silicon remover.
There are several different makes of luggage,
the links below are reviews of Oxfords top of the range but their bottom of the range is much cheaper and similar.
Some things to look out for is if it's expandable,
can carry a full face helmet and if it converts in to a rucksack when you get off the bike.
http://www.webbikeworld.com/r2/motorcycle-luggage/motorcycle-tail-bag.htm
http://www.webbikeworld.com/r2/motorcycle-luggage/motorcycle-saddlebag.htm
http://www.webbikeworld.com/r2/motorcycle-luggage/motorcycle-tank-bag.htm
Seat bags often have 2 bungee cables and a strap that goes under the seat.
The instructions often say that you must use the 2 bungee cables and the strap together for safety.
I can only see the need for using both if you are on a big bike at over 70 mph
with a lot of weight in it and going round a corner with your knee on the ground.
The main reason I can see for using the strap under the seat is to stop someone stealing the bag.
The 2 bungee cables take only a very few seconds to take on and off the bike,
they really hold the bag down and stop it sliding forwards, backwards and sideways.
If you do not have any luggage mounting points on your bike,
you can also buy universal longer bungee cords to stretch to foot rests and other places.
Some seat bags have bungee hook rings on top of the bag as well;
the instructions say they are to strap the top of the bag to the bike when carrying a lot of weight.
I really cannot see them as being necessary,
but they could be used to strap something large and lightweight to the top of the bag.
Anti Vibration Handlebar Devices
See Anti Vibration Handlebar Devices page.
Seat
You can buy seat pads but first try standing up every time the bike stops even for traffic lights,
try taking small roads with many tight bends.
The faster you travel the more you will move around reducing seat and leg problems substantially.
For seat pad reviews see
Five Motorcycle Seat Comfort Pads Compared - Motorcycle Cruiser
(Roho Airhawk is available in the UK).
I have read that many people get a normal sheepskin wool rug
and cut it to size and fold the excess underneath the seat to hold it on.
Untried and untested ideas are an envelope you post delicate items in (has bubble wrap inside),
gel computer mouse mat or even polystyrene.
There are padded pedal cyclist shorts and other padded clothing for people who have trouble sitting in normal chairs.