My space heater is a sears model 600 and I don't get enough heat coming from it, the thermostat I have on my wall only goes to 90 degrees fahrenheit is there a certain kind of thermostat that belongs with this model 600 space heater to give a higher setting to get more heat?

The thermostat is not the problem. If you could set it for 150 degs, the heater still would not heat to that temperature if it can't make 90.

Thermostats just turn off the heat when the set point is reached. Set at 90, it would turn off when it was 90 near the thermostat then back on at 3-6 degs below that.

Several questions come to mind.

1) Did it ever heat the same space adequately?
2) Does it use a fan to circulate the air, if so, is it working?
3) Is there a filter, if so, is it clean?
4) Is this a gas or electric heater?
4a) If gas, has it been serviced to be sure there are no nest in the flue stack and that you are getting the proper burn.
4b) If electric, are all the elements working.

As you can see, there is a lot that can effect the heat output.

Now remember, this is without knowing your system or usage.

If you have more information, post it here or drop me and e-mail.