Hi tlk, welcome to myBulova. I am the guy that gushes on family heirlooms and yours is over the top. To think that you have the watch that you father AND your grandfather wore is amazing, congratulations to you!
I think you're spot on with the ID. This is a tricky era as Bulova was advertising Clipper, Sea Clipper, Royal Clipper AND Yankee Clipper. I agree with the Yankee Clipper based on this ad:
I don't recall ever seeing a Bulova Box specifically labeled for the Yankee Clipper and would suggest you look for something from the era. In terms of band it's off to ebay for you. There are several watch band, strap bracelet sellers that specialize in period items. One of them, "Timesofplenty" is a member here. The lug spacing will help you narrow your search. It really is personal preference as to leather strap or stainless band, either is appropriate. At the point of sale it is possible your grandfather had the band removed and a strap installed.
Oh, one more thing, it is possible to have the dial restored on your watch. I will look exactly like it did when it was new. As you've replaced the crystal and had it serviced I assume you'll be wearing it. the dial restore would make it look very nice.