There are many stock bow rollers that will fit. Generally I think it is usually a mistake to mount oversize gear on any bow partly because you don't really need oversize; but mostley because catilevering the roller assembly way out from the bow plate creates bad leverage on the bow plate you have bolted the thing to when the boat is pitching at anchor. I chose an obsolete Ronstan fitting because it was the smallest that would hold my 25lb CQR. It projects only a few inches, and has enough plate on the back end for me to drive five bolts into my bow plate, which I drilled and tapped. This shot shows the roller I installed. It is made fast with five 1/4" studs I tapped into the bow casting.
Wharf vultures at my club came by while I was mounting it shaking their heads forecasting that I would wish I had mounted a bigger and longer one... I have to wonder why. The one we have is massivly strong, doesn't spoil the look of the boat and does the job well.
The anchor looks precarious but in fact it is rigidly secure, and held with one line holding the crown of the anchor with a snap hook, an single hitch around the anchor roller and the anchor's shank, then making fast the forward part of the jackline.
Looking at our anchor set up bows on... The line threaded through the shackle on the crown of the Bruce anchor serves to retain the anchor in the roller... it is utterly secure and can't move no matter how hard Surprise pitches. Making it fast in place is quick and easy.
Beneath the shank of the Bruce anchor you can see three of the five 1/4" studs and bolts that secure the anchor roller to the bow plate.
Looking aft you can see our Lofrans manual windlass. The chain running over it is 150' of 5/16" BBB. to the right of the windlass you can see the rope deck pipe through which runs the end of 200' of 5/8" three strand nylon rope; down below we have our forepeak divided into two halves. The chain falls under the windlass's gypsy in the starboard side, the rope to port. I keep a 3/8" bronze bow shackle in the spliced end of the rope ready for attachment to whatever anchor we may use there.