4 week old christening outfit???

[The[cookie]Doctor]

Bubs is going to be four or five weeks old (at the most!) when the baptism rolls around and im struggling to think of what will be suitable as a christening outfit.
I need to start thinking about getting it now because EVERYTHING looks like it costs a fortune, but have no idea really what to look for...

I trawled around on ebay for a bit and found a white silky romper that looks a bit like a tux - it's cheap (well comparably) and can get in a 000. Should i just gamble and get it?? Would i be better of buying material and trying to convince my grandma to sew us a gown?

I never realised it would be so expensive and if it hadnt have been booked in for so long i wouldn't bother yet, but we have an easter baptism booked and it'll be with my sisters as well (who will only be 12 weeks) so i'd like to still do it.

BTW it will be a catholic ceremony if that makes any difference.