You have much more guts than I do lol! No way I would've spent that long in that area when I was doing that.
The first one I bought that wasn't my mom's or something I stole (bad me

) I got from a 24/7 supermarket because they were 24/7 and because they had those automated check out lanes so I could do so w/o getting "caught". During high school, would sometimes sneak out of my house at like 3 am (mom stayed up late...how inconsiderate of her!), walk a mile to the store, walk around, ditch the undercover security guard they had, run over to that area and basically grab w/e I noticed/liked during my initial "recon/ditch the security guard" phase lol, then check myself out, pay and leave asap lol. Didn't bother looking at sizing, just grabbed w/e looked cute or unique or different.
You could try water balloons until you get some breastforms, those were prolly my favorite things to use as boobs. They are squishy, have some weight to em, bounce, all that good stuff, and as long as you don't make em too big, shouldn't have to worry about having em pop.
Winter is the perfect time to wear em outside indeed! Last winter I think was the first time I think I started doing so. At least there's one good thing about winter and being freezing cold all the time.