Try searching for something along the lines of "Reverse Thrusters" on the addons page. If not, here's how you can do it.
1. Since your a Windows user, find and download EVNEW if you haven't.
2. Open up EVNEW and create a new plug-in.
3. Create a new weapon resource. To be safe, I'm going to arbitrarily suggest making it ID 400.
4. Set guidance to "unguided projectile", or -1 if it only has numeric selections.
5. Set count to 1
6. Set reload to 0.
7. Set graphic to 0 (mostly as a safety precaution).
8. Find the box that says "Is a secondary weapon" or something similar and check it.
Now you have two methods...
9a. Set speed to a value like 900. If the weapon doesn't work, try lower speeds. If it launches you in the wrong directions, try higher. Put impact to a very high value, like 6,000. Set the blast radius to something small, like 10. Then finally find the box that says "Blast affects player" or something similar and check it.
Or.
9b. Set recoil to a high value, such as 6,000. Note that this results in somewhat different behavior from the other method. I've never made a reverse thruster myself (though I know how), so one may be better than the other.
10. Click the "OK" box and then save.
11. Create a new outfit resource, I'll arbitrarily suggest 600 to be safe.
12. Set one of the four outfit types to weapon.
13. In that field for the weapon, put in the ID for your weapon (400 if you used my suggestion).
14. Set tech level to 1, availability to 100. You could use different values to make it more rare, but I'm assuming you're not wanting to go hunting for it.
15. If you so wish, you can now set the other name fields, a desc, and outfit picture. Though since those are optional, I'm not going to cover those.
16. Save.
17. Drop into your plug-ins folder and run Nova. If there are no conflicts with other plugs, it should work and you should see your outfit in most outfitters (Fed space at least).
That seems like a bunch, but it can be done in five-ten minutes easily, if even that long. If you still have any question, ask away at the Dev Board.