It sounds like almost any small to mid range compressor may work for what you need. The big issues to consider are, will you want to pump nitrox in the future (continuous blend), if so some types of compressors work better than others, in particular stay away from the Rix oiless units, and the military surplus stewart warners due to lubrication issues, you can do a search on the issues. You say 125 - 150 fills per year, what you don't say is how many tanks at a time, as to fill speed even the smallest 3.4 CFM (some getting as little as 2.9 CFM (174 CF/Hour) real world air flow delivered to the tank) compressors will meet your delivery requirements. The problem is a lot of the smaller units are not rated for continuous duty and are only rated to fill 3-4 tanks at a time without a break to cool off. With that number of fills per year the shelf life/CFM capacity of even the smaller filters will not be a major issue (need to be changed every 30-50 tank fills at $45), still a larger filter may be economical As to the the 3500 psi working pressure, this should be within the range of all continuous duty compressors (they were designed to fill 4500+ psi bank cylinders) and close to the rating on many older portable ones. My 30 year old Bauer Purus 3.4 cfm portable is rated to 225 bar (3307 PSI), it was also offered in a 300 bar high pressure model. As to brands it seems almost all are good, some are just better than others, new portable compressors units start around $3,000, good quality used units can sometimes sell for under $500 ( I paid less than that for my Purus, but had to drive almost a thousand miles to pick it up, and have spent more than I paid for it to add modern filtration, new motor, etc). If you have the space for it an older mid range 3.5 - 7 CFM continuous duty units (weighing in around 400-450 pounds) may be the best deal as they often sell for only a little more than the price of the portables and often have far better service histories and duty life. Parts availabitiy may be an issue on some of the older units particularly those from the smaller brands, however if you stick with Bauer or companies like Mako that tended to use Bauer blocks parts for most models will be easy to find, some of these blocks had production runs of over 20 years and were just recently replaced by new models.
Ike
p.s. most portable compressors only have manual drains which, require constant attention during tank fills having to be be drained every 10 or so minutes while running, many/most continuous duty models have automatic drains which allows you to pay a little less attention to whats going on.