With the stricter emissions controls imposed in the US in the 70's and 80's, Mercedes phased out the use of carburetors here before the 190E was brought over in 1984. Even in Europe in the mid 80's when the "Green Party" pressured the big German automakers to offer the same emissions control performance in the Fatherland as they were providing to the US market Mercedes did not offer carbureted engines with emissions controls in Germany as the technical direction for the US regulations had already led away from the use of carburetors. So, to answer your question, you would be hard pressed to find a 190E anywhere with a carburetor anymore, and if you did you would be really hard pressed to get permission to bring it into this country for normal road use.
I have a 190E 2.3-16 from 1986 that was a European version. I bought it new and federalized it here. The job was relatively simple as I ordered the car with the US emissions system. It is slightly different but passed the testing required pretty much "as-is" and has been an excellent daily driver for nearly 16 years. It has 199,000 miles, is a 5-speed manual, and has relatively little of the extra stuff Mercedes loaded the car with for sale in the US. In Germany all the equipment in the car, other than the very basics, were options. Anyway, I have seen a number of them for sale on the 'net for around $10K that look and sound like well maintained vehicles.
The plain 190E as far as I can tell, and I know people with these cars from 1986 and 1987, including the Diesels, have found them to be exceedingly reliable and sturdy. Basically an excellent example of Mercedes design and workmanship. So, look for a while and be choosy, and good luck.
By the way, the prior 300E body style came into being in 1986, and cost about $10K plus more than the 190E at the time. It is unlikely you will find the same quality car for the price range you specified in a 300E. But they are also very available on the 'net and dealerships.
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)