Let me know if you get stuck - I've got the old ones from a headlamp change (cracked lense and flakey reflector), knocking about 'somewhere' I could dig 'em out for you and you can have 'em for postage....
Or, failing that, why not 're-enforce' the current ones - just put a fuel hose clip around it and tighten til 'snug' (not too far or youu'll crack the 'arms' off it), after teh lamp is in properly - it wont go in if you fit the clamp before..........