I need help with slips.......

I went to Blum's yesterday and got all the stuff for under my dress, but I still need a slip.. my dress is a ballroom gown and I need medium crinoline.... I really didn't want to buy it where I got my dress... I think it will be an arm and a leg...

anyone have any ideas for me?

I bought one on eBay and I am hoping it is the right kind!