If you are of the mind, use you fingers. You can use one finger (middle one works best) lube it up good, insert and use a "come here" motion. Make sure he is aroused or do this while you are giving him some oral or hand work.
Toy wise, I would need to know what size he is comfy with. But pretty much any toy with a G-spot type curve could work good. Same thing though, arousal is key to P-spot pleasure.
I would say a smaller toy 4 inches -5 inches or less. I have tried the fingers but not the middle I will have to try that one--Thanks for the advice I appreciate it-
Is that the length or circumference?
As far as fingers, you need to get 1-2" inside. With my middle finger I can reach the top of mine, but my fingers are long. The wifes, on the other hand are short. So she has to use the middle one just to get about half way up it.
The finger is best if it goes in all the way. Make sure your nails are trimmed and filed, and if you can get two fingers in it feels even better. Start off stroking and with gentle pressure instead of pressing hard, because that can get uncomfortable.
After that then you can look into getting a soft toy with a curve.
If you're uneasy about putting your fingers in there, go ahead and get some gloves. Latex (if there are no allergies) or whatever your doctor uses. IF you try with your gloved finger and he enjoys it, you can invest in one of the anal douches so that he's more clean (which makes his enjoyment greater)