This is true; it's a slow time of year for selling plants. And the USPS has been doing a really awful job of delivering lately...I've been getting record DOAs because it's taking them 4-5 days to deliver priority mail packages, during which the 72-hr. heatpacks die and freeze the plants. I've pretty much just decided to avoid non-local sales for at least the next month and wait 'til the weather improves. I think a lot of casual plant sellers are doing the same... especially the ones that don't have heatpacks on hand.
All that said, I think the best way to get your hands on some plants might be to look into whether there's a local aquatic plant club wherever you live. Plant club people are typically very nice, generous, and enthusiastic types who're happy to provide inexpensive plants to new hobbyists.
