I just got fuses I needed for my B&K from mouser electronics
1000 north main street Mansfield tx 76063
contact Matt Bell 817-804-3800
shipping was like 5 bucks iirc,
and they where over packed, plastic ziplock type bag, wrapped in bubble wrap and then in a box. overkill if you ask me.
City electrical supply in Brockton has a ton of different fuses, but just didn't have what I needed as mine called for a dual element slow burn/blow fuse and the only one they had that crossed to it, was a single element slow blow might try giving them a call as they are only 20 minutes from you
you try ralph pill in Dorchester or yale electric in Dorchester right off 128