I got on to some plain race jerseys but they only come in red/black arms, white/blue-black arms or a grey/black arms.
They are very good to ride in though and soak up the sweat well and can be screen printed as we have done.
As for helmets, the best I could think of was those helmet covers the youngsters had a few years back, similar to what speedway riders use to show which team they're on, however the supplier only had a few left and they were too abstract as well.
I would just buy a plain helmet but the only one available was a Shoei for over a grand!!