Forgot one technology (because I've never used it) that might work - Guided microwave or "radar on a rope" that shoots an RF signal down a probe, where a reflection bounces back off the medium.
Never having used it, I'm not sure what would limit its application, whether foam or precipitation...
I use an instrument distributor's site (www.lesman.com) for budgetary numbers, precisely because pricing is available without waiting for a quotation.
Our plant uses a fair amount of Honeywell equipment and you mentioned that brand, so it might be a fit for you.
Bud
