Check the ASC spring chart
fo guidance here. While the springs were tested with a highly upgraded TM P90, I've found the readings to be a good base line for an otherwise stock TM M4 with whichever spring installed.
A PDI 120 might do the trick, but PDI were kind of flakey a while ago with a lot of guys getting mislabeled springs. A Prometheus M90 wil do the trick. Not sure of Modify or Madbull as they haven't been put on the chart. Springs are an easy change if you know what you're doing. Chances are, unless the retailer you got the gun from offers a gundoc service, you'll have to purchase the spring and have someone install it for you if you're not comfortable doing it yourself.