R34 Skeg Bronze bolts

Supplier needed

Hi all, I’m trying to replace the 4 x bronze bolts which secure the rudder shaft fitting to the foot of the  skeg on ‘Villager’ R34. I’m struggling to find a supplier. The bolts are 3 1/2” long x 3/8” dia in imperial measurements. I believe a metric equivalent is M10x90mm, but I’m told that I’d have to go down the 316 A4 stainless steel route if I chose these metric dimensions. So, I’m asking for your help-do you know a supplier for these bronze bolts, or, what do I have to look out for in terms of corrosion if I use this (marine) grade of stainless steel for use below the waterline. All advice would be most gratefully received  the