Gar,
I bought mine on-line from "McMaster-Carr" (my Local Address is 9630 Norwalk Blvd., Santa Fe Springs, CA 90670-2932 Telephone = 562-692-5911 and web address is = la.sales@mcmaster.com). They do have multiple locations though.
McMaster-Carr lists their Drill bushings in the 'hardened steel' category by Decimal size and by designations such as letter, number, fractions; but their Metric listings must be converted to "Imperial Decimal" number values by the Buyer.
The sizes i ordered are the following:
.25" ID marked U 1/4, .257" ID marked U F, .2656" ID marked U 17/64, .272" ID marked U J, .277" ID marked DB I, and .316" ID marked U O.
They do provide Custom sized Drill Bushings; but the prices are about $40-$60 range for the one I will be ordering for .246" or .247" diameter. Also, the custom order process requires ID, OD, Length and the Tolerances on each dimension to be stated.
You may find some of your needs are listed as undersize or oversize ID bushings also.
They also have unhardened 'finish yourself' bushings so you could work them to the exact size you need and then Heat treat them.
By the way, have you done any more with your .25 Stevens experiments?
Best Regards,
Chev. William