Here's the closest one if a Tiger Musky is ok rather than a Pike.
Justs north of Ft Collins you have Wellington #4, then Smith Lake, Milovak Reservoir (near Firestone) and North Sterling Reservoir
A bit west you have:
Stagecoach and Williams Fork
Going south and west you have Eleven Mile* and Spinney - (*one of my favorites)
And if you are up near Craig, hit the pond across from the rest stop outside of Craig (all the Yamapa Pike were put in here and other ponds,
Rocky Mountain Pike | Sportsmans News
-----a great and recent article on fishing for Pike in Colorado.
Colorado Tiger Muskie Fishing - Tips, Records & Stocking Info by Fish Explorer
----- a superb source for finding where fish have been stocked where. About halfway down the page to the right scroll to Tiger Musky or Pike and all the lakes come up!
Good luck on getting him out and into old Esox!