[Richard Merchant]

Nick’s suggestion about Lee’s Electronics is very good (not only because I love them – lots and lots of bits, and very reasonable prices…).  They have antennae:

https://leeselectronic.com/en/search?controller=search&s=antenna

They are not a radio store so whether they can provide knowledgeable advice I don’t know.

If a reasonable secondary product can be located, I’d still be concerned about water-proofing and would stick with my silicon suggestion…