RTV: room-temperature vulcanizing can refer to silicone, which is good for sealing, drying rubbery at room temperature. Styrene is a plastic, sold at the hobby shop in sheet form, for forming structures and surfaces. Epoxy is used as a glue but I'm not sure of its range of applications.

Subs in the hobby shop...here in Texas...good luck. Maybe a few models, I'd guess.

By the way--at Hobby Lobby, models and r/c are a tiny part of what that store sells, the models are generally one aisle tucked away in the back while the home decor, fabrics, and crafts are center-stage at HL. Yours may or may not have r/c gear.

But if you're lucky enough to have a Hobby Town nearby-- those stores are small, but r/c and models nearly fill those little stores.