You sound just like me a few months ago!

After a lot of looking around, I eventually bought one from the US via ebay from some place called Poorfish. A Humminbird HDR610 with inhull puck transducer, it only does depth but does have shallow and deep alarms and a keel offset option. Depth readout can be in feet, metres or fathoms. There is also a transom mounted transducer version for the same price if you're minded that way.
I've installed it and wired it up. Still need to calibrate the depth and set the keel offset but it seems to work ok. Total cost including shipping was $150 (in proper Australian money!) and I had no dramas with the seller.