I'm very new to bjd's so am not the best person to advise you - however I'll try to help!
Have you been on Den of Angels forum? They have databases and lists of dolls which might help.
How big is potpourri?? Measure her height, head circumference and foot length and width and perhaps someone can direct you from there to the right stuff.
If she's around 60cm she's SD, if she's around 43cm she's MSD and if she's less she's a tiny. I know of quite a few tiny sites now having been researching them so could point you in their direction.
On Audreys dolls
http://www.audreysdolls.com/index.cfm?Products=products there is a guide telling you how to measure your dolls head for a wig. There are also wigs etc for sale on DoA once you've made 40 posts.
Hopefully someone more knowledgeable will be along to help you soon