The OE elbows are chrome plated steel and are usually pitted. LockDoc shared a thread with some possible aftermarket alternatives for both elbows and mirrors:
Elbows, 4.5” even offset
Signal Stat 7933
Truck lite 97869
Napa LIT 97869
Mirrors
Truck lite 97805
Signal Stat 7053
Other part numbers
97842
97681
By the way, all of the hardware can be found at
http://www.boltdepot.com, and costs about $25 shipped.
Needed to rebuild one pair of mirrors:
*(8) Nylon Washers - .406 x .94 x .06
*(10) SS Plain Washers - .406 x .88 x .06 (Varies depending on washer thickness and stud length)
*(4) SS Lockwashers - .406 split
*(4) SS Acorn Nuts - 3/8-16 UNC
*(6) SS Washer Head Screws - #14-14 x 3/4 with .515 washer
*(6) SS Internal Tooth Lockwashers - .281 ID (if you want to use under attachment screws, but probably not necessary)