Knob sizing for Lakland JO??

So I've got a Lakland JO-5 and wanted to replace the regular plastic J-Style knobs with some rounded P-Bass chrome knobs. I had a guitar center gift card so I grabbed some the other day but they did not fit! I assumed that the sizing of these things would be universal but maybe I'm incorrect? or maybe the ones I bought were some cheapy ones of a weird size? I also called lakland and they measured out the knobs they use and said it was a pretty regular size.

Does anyone have any experience changing these / could give me some info on where you purchased them from!

Thanks guys!