Try MS Colour, The Camera Workshop, Ruby Foto, TK Foto, John 3:16, any more guys? Should be able to find that step-up ring. Or look in the Buy and Sell forum...
BTW, can't u use two steup rings? Just asking for interest sake? Like 49-52 and then 52-62mm or something like that.... and btw, muko, have u tried 52mm filters, does the camera still vignette?