Well, when I bought one for my DD 7 years ago it was a rather bulky, functional, albeit a bit ugly, bag that matched the pushchair. There really wasn't much choice back then. I used it to death and its beyond use now so I will be looking for a new one too.
My SIL turned up with her newborn last week sporting a rather lovely Yummy Mummy bag and I was soooooo jealous. Like, I want one, now! But the price tag makes it a definite no-no.
So, on a tip-off, I will be spending a lot of time at TK Maxx in the coming months keeping my eyes peeled for a lovely expensive looking bag with a moderate price tag. Fingers crossed.