Cool watch, thanks for sharing your treasured heirloom with us. The case markings seem to indicate it was assembled outside the US. Serial number starting with a "stand alone 3". It is curious that it doesn't bear a date stamp. The illustration below is from the 1976 Bulova Linebook0200. This is the earliest reference I find, so I would be inclined to assign it as a 1976. It falls in the "Automatic Calendar" section and is only assigned a model number.
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1976 Bulova Model 11543-6W
The band is generally referred to as "President" style. I would search eBay (president watch band) armed with the Millimeter dimensions of the links. It is entirely possible you will find individual links (pricey) or an identical generic replacement or for a different brand that will work. The most important measurement will be the width of the center link to fit the "lug" on watch case; followed by the overall width at attachment end and clasp attachment. It could be possible to cannibalize a newer band for links.