If you have stripped a number of B-Screws, you can find replacements by searching for the following specifications: 

Cylinder Head Connector, Confirmat, Hex Socket, 4 mm, Bronzed, length 50 mm, Ø 13 mm (Supplier Website)

Or: CONFIRMAT ST BZD 13MM HEX 4 7X50

A 4mm hexagonal drill bit is recommended. A 3/16" hexagonal drill bit will also work if you do not have access to a metric bit.

Do not use more than 5lbs/ft of torque when installing these screws, or you may risk stripping them.

Replacement Rack Rails

3U Rack Ears

https://www.reliablehardware.com/pairrackrailsfullholepre-cut3space525incheslong.aspx

Rack Ear Specs

· 1/8'' Thick Steel (11 ga.)

· 1.55'' x .68'' x 5.25'' Long

· Tapped with 10-32 Threads

· Black Powder Coat Finish