Any suggestions for a muzzle device for 45acp?

A rifle in 45 acp doesn’t have any perceptional recoil 

Use a linear compensator:

https://www.joeboboutfitters.com/40S-W-45ACP-10MM-...

I infer from you question that you plan to put telescoping optics on your rifle (because you are using offset sight/red dot).  Why?  Pistol caliber rifles are most practical at less than 100 yards (or much less) in red dot or iron sight range.  Your primary sighting system should be for the primary range of the firearm.  If you want a little more magnification for a little longer range, they try a red dot with flip-up 3x magnifier.

Additional info: You didn`t mention what .45acp rifle(carbine) but just for example let`s pretend you are talking a Rossi Puma lever action .45Colt/.454Casull with 16" barrel and you want sub MOA which is a great barrel to experiment with by porting. There are no threads at muzzle nor gas port... just barrel. Comparing the same length barrel with .223 barrel you have about 4 1/2 times the volume of dead air in front of the bullet that is pushed out upon firing. A correct porting starts working to stabilize the barrel ahead of the bullet as well as hot gases pushing the bullet before leaving the barrel. Although technically speaking.... porting is often stated that it does not reduce actual recoil but does reduce somewhat of a relief to the shooter, however, that is solely my opinion. I do know that a Rossi .454Casull with correct ports can reduce the felt recoil to somewhere between the .45Colt and .454Casull. Don`t confuse the port design I am referring to with porting done on barrels I have seen with round drilled holes close to the muzzle(disregarding the breakthrough location into the rifling) Only EDM can make elongated slits to break into the grooves (not lands) and follow the helical angle of twist plus angle of exhaust to outside of barrel. The machining is done while accompanied with a flow meter to balance flow from each port.

 Finding that person that can produce and follow what I am talking about may take a while but according to my interpretation of your demand for accuracy you may consider. 

Porting is the only thing that can help your problem IMHO. I had a really good port design several years ago that reduced recoil when I was surrounded by machines that could produce the complex design on pistol barrels. If you can do a little research to companies like Wilson combat or names like Turnbull you may discover someone that can help. Those machines are EDM (Electric Discharge Machine) electrode type. Not wire EDM. Index timing has to be right on and electrodes have to have the correct angles to influence the escaping gases to actually push the barrel forward countering the recoil while concurrently and precisely dispersing the gasses to steady the muzzle. The design cannot be done with conventional machines that cut metal like milling machines and lathes. 

EDM machines metal by bombarding (eroding) the metal with electricity in a dielectric fluid shaping the port like the copper or graphite electrode that has to be either handmade or CNC cut.

I don`t think anything that screws on will help like an extended barrel with ports.  

And why would you need to reduce the recoil on a 45 ACP rifle?  When my youngest son was 8, he could shoot a 45 ACP pistol single handed.