Square Taper Spindle - Mongoose Dolomite - Replacement

[yuckfoo]

Looking for a tip on purchasing a new spindle for my Mongoose Dolomite. From what I can tell these are in the $60.00 and up price range. Hoping someone can help me choose the proper spindle so I get it right the first time.

 

[yuckfoo]

Mongoose sells the part for $5.00 but the prices I saw online were $60.00 and up??? Mongoose says the part is on back order (end of March.) I don't want to wait that long.