Porting would be my first suggestion followed by a different set of grips. There are two thoughts towards grips; first is to use the rubber ones as they are thought to reduce recoil similar to a recoil pad. In some instances this appears to be true but in others the rubber "grips" the hand too well and seems to enhance recoil. The second option is the exact opposite; wood stocks with no checkering. It is thought this will allow the gun to slip in your grip and not transmit as much muzzle flip and thereby reduce recoil. I have found both to work depending on the gun and load used. Sometimes it can vary with the same gun depending on the load and how many rounds one shoots at a time. Other than the porting, it will require trial and error to find the "right" stocks.
I have a pair of shooting gloves that are similar to the Cabela's ones. I don't like them that much as they change the grip dimensions for me. I swap stocks around until I get one that I like, wearing much more than a set of light weight gloves generally throws the "feel" off for me. I found them helpful with my Striker at first until I got the Bondo out and formed the grip to my satisfaction. Others I know swear by them but as for me, I can do without for the most part. If one has the money and inclination, there is no harm in trying them out.
A set of the rubber Hogue grips might help you a little ( but 30% reduction is a bunch ) and it won't give you anywhere near that much.
When I shoot my .44 mag - I do wear gloves - but they are winter golf gloves (the fabric kind). They sell them in pairs - footjoy and others. They give a good grip to the gun - but still real flexible so no trouble loading, etc .
But I doubt combined the grips and the gloves will give you more than a 10% reduction. I have some nerve damage in both arms and hands / and a lot of arthritis - but I refuse to give up shooting and while I've lost about 30% of the grip in my lower 2 fingers in each hand - I manage to get by with these gloves (and advil) which doctors don't want you taking too much of. But on really bad days - I shoot a .22 or in the case of shotguns I go to a semi-auto or to a 28ga and leave the 12ga alone. Some days are better than others - I hope this helps a little. Despite these issues - I refuse to give up shooting. Good luck with it.
When I had bones in my right hand replaced with steel, my doctor suggested I buy a weight lifters fingerless glove to use when handgun shooting. It is padded and has a strap that goes around the wrist. It is a "Lee Haney". It worked so well, I still use it, even when I am handgun hunting! Many of my friends went and bought one to use......Regards, James