How to keep baby warm without Halo sleeper

Hi,
My son is 10 mos old and is crawling and pulling up. We stopped using the Halo sleeper months ago (it was summer anyway) but now I feel he's too cold with just a sleeper on and no blanket, even with the heat on at night. I was wondering if anyone had any suggestions? I don't think getting a new Halo sleeper will help as how will he stand up and move around? I have 2 more months before I can use a blanket so any suggestions would be great!

thanks,
Lauren
(whose trying to figure out how to change her user ID - I am a mother, not a soon to be mother - LOL!)