1.. measure the steering Tube on the stock fork.
2... look for a used Marzocchi Bomber fork or Rock Shox Air fork on Craigslist or Ebay or where-ever... make certain it's within about 1/2" or so as long as your stock fork. ( i've found some great deals on Rock Shox SID forks too!)
3... don't get greedy with the fork TRAVEL since you only need about 80 to 100 mm travel unless you want to jump off cliffs...
slap that sucker in the frame.. i know you can do it.
4... ignore the trolls
(you could try a Bolani fork.. all over Ebay and Amazone... they had some seal issues but i've heard that got sorted out... low cost air forks... a 29" will work since 29" and 700c wheels are the same Bead diameter....)
5... Put phat CX tires on and go slam some drops. keep yer butt back and your knees bent !
example:
https://www.ebay.com/itm/25604210143...Cclp%3A2047675