I would 2nd what jdmaris said, though I don't know a lot about those, some of those models fit the small size category. Another handy feature would be one of these with a 3 pt. hitch.
I think the important thing about looking at an old crawler is to be able to assess it's condition, it would be desirable to find one with a decent undercarriage, you can get a lot of part time use out of one that is worn, but if the adjustment is all the way out and the wear is starting to accelerate, or it will toss a track off easily, you want to avoid that unless you have the money and resources to rebuild it. I've seen those models JD mentioned, some with 3pt hitch and a wide gauge, but small, just right for little work.
What was mentioned below is true of the older Caterpillars, if you find one of those in decent shape, might serve your purpose, but the smaller ones like a D2, D4 etc. will have a dozer, many were also just drawbar ag work, no dozer tractors further back the older series like a Twenty Two, Fifteen, Ten may also fit the work you want to do, but they usually do not have a dozer kit, you would have to fabricate one, tractors like these were not designed to have them anyway, but I've seen a few with them, just have to take it easy.
It seems there is a lot of nice ag crawlers in CA., pretty reasonable too. You still have to assess the condition of same, there seems to be a fair amount that don't need a total rebuild, still have salvage yards and other resources for parts, so an older caterpillar in decent shape can work well too. You can't beat an old D6 or D7 for farm use, lot of em around, you just have to make sure it's not worn out. A late 50's mid 60's D6 is a great tractor, vegetable farmer/greenhouse guy near me, rebuilt one, spent a fair amount on it, but having gone through it, it will last him a long time. Even a small one can be a real handy tractor to have no matter what you are doing, hopefully you find one to look at and can determine it is in decent enough shape for your use.