Tim,
Sorry I didn't answer sooner, I'm on vacation and was staying off computer! You should be able to order the "boots from a Sundance Dealer. We get them through Sundance but they might be available through other sources (If anyone knows, chime in!) aftermarket, I've never looked.
You can also get a 2 part foam pack from almost any spa dealer to re foam but you have a ways to go before that so, do your digging and gluing then water test. If everything is OK let us know and several of us will point you where you need to go for inexpensive foam packs.