why would you want coolant temp only ? your comp will flash the engine light on and off if your temp gets to high and it will stay on if your really gettin to hot.
check out koso EGT gauges with the coolant temp option but i wouldn't say its inexpensive.
If you really want to know whats goin on with your motor get EGT's but on the other hand if your sled is stock and you dont plan on doin mods then you wont need a egt set up just ride the thing if thats the case.
Another vote for KOSO, I have there super slim thermometer. Its roughly 2" wide, 1" tall. The blue light is very readable in the sunlight. Very impressed with the gauge for the cost of it. It mounts anywhere, I paided $45 bucks for it.
There was a person at Allen creek last year that showed me that you can scroll thru the gauge and there is a temp setting. Can't remember the exact sequence hold one button tap other one etc it showed up number 8 I believe and it showed the temp up in degrees. I thought I knew all the good tricks for the m series sleds just goes to show you can always learn something from someone.