you can get a Navman 4430 from whitworths for $219. I little out of buget but whats $19 in the scheme of things ?
I has good resoultion, shows water temp, depths etc. No speed function
but it does show you battery voltage which is handy. It's a sweet unit my dad has a 4431 (speed version) in his boat and it is an awesome little unit. I am getting the 4430 for my yak sometime next week 
I has good resoultion, shows water temp, depths etc. No speed function