You just gotta keep lookin, for one of those 1 3/8 taps.
There's one on ebay, right now for $17.00
tap 1-3/8 -6 thd hss | eBay
I have bought those taps, for as little as $12.50 in the past, from e bay tool wholesalers.
Now i have a collection of them, in the toolbox.
Jim V.
hemi71x