The bolt is one of the ones call "C" in the picture below that supports the guide rail on the side of your bumper -- it can be replaced with a stainless domed head allen screw or a "v" shaped flat head stainless screw from a local hardware store or if allen headed metric isn't available locally you can get it from the internet source mentioned below:
When you look under your fender you see that the available real estate has been encroached by some large protruding fasteners. You can remove some of them and replace them with stainless steel flat head and pan head socket type fasteners from:
http://www.boltdepot.com/product.aspx?cc=25&cs=82&cm=19&cd=1318The list of possible replacement fasteners goes like this:
Item # C
Product #6698
Metric socket flat head screws, Stainless A-2, 8mm x 1.25 x 16mm
Quantity: 4 pieces
Price: $0.54
Subtotal: $2.16
Item # B
Product #6702
Metric socket flat head screws, Stainless A-2, 8mm x 1.25 x 35mm
Quantity: 4 pieces
Price: $0.73
Subtotal: $2.92
Item #A
Product #6657
Metric socket button head screws, Stainless A-2, 8mm x 1.25 x 25mm
Quantity: 4 pieces
Price: $0.96
Subtotal: $3.84
Item #D Welded Nut
Shorten slightly with 4" grinder
Overmold (blend a hump) with JB Weld Epoxy
Paint with silver touch up paint
Item #E (not shown) Mounting bolt for Right Buddy Peg
Shorten slightly with 4" grinder
Paint with black touch up paint
You will need to buy a HSS countersink to countersink the flat headed screws to be nearly flush to the sheet metal that they will retain. Close to flush, but not completely flush. You do want some metal there to clamp up to, right?
Go slowly here == making the countersink too deep & large means you won't hold the sheet metal in place and that is a classic "bad thing" when trying to hold stuff together with flat headed fasteners.
The main fender mounting bolts get replaced with shallow pan head fasteners instead of flat heads. Why pan heads? You got these protector bumps in the sheet metal and all you really need to do is get shorter than the bumps. Pan heads are stronger than flat heads and the fender is a structural element that sees strong vertical vibrational forces and potential tire/fender impact forces. It needs more fastener strength than the horizontal mounted gingerbread stuff that we flat headed for width clearance.