For the helmet holder, what I did was take the two helmets down to Clarke Rubber and got them to cut out an 8inch thick piece of foam so that the helmet sat nicely into it. The use a 1inch piece of foam and join to on the base or if you really want to go the whole hog, make up an aluminium box to put it in and bolt that to the floor in the rear. Total cost: $20 bucks!
Also check out www.seemore.com.au for some cost effective prices on new gear. I haven't bought anything from them but their prices are good and they are supposed to give good service.
Try www.bmsc.com.au/forums for the terratrip and all of the other stuff too.