Howdy WaddWatson,
I understand; I've been shooting SASS for 15 years +, often with period correct (as close as I can get them!) outfits, and I KNOW the vast majority of my fellow shooters have no idea how accurate my outfits are, or how much time, money and effort went into putting them together.
As for Californio type spurs, you have looked at the Garcia offerings, yes?
http://capriolas.com/catalog/index.php?cPath=39&sort=2a&page=1My guy uses E. Garcia ones as well, and has some fairly straight shanked ones that work on his low heeled ropers.
Another possibility are the Californio offerings by Vogt. These are very good quality; I have a pair of 893s with the other side being 889B (with the addition of sliver overlay on the raised design) that have worked well when actually riding.
http://lesvogtscalclassics.com/SpurGallery.htmlClick on 'classic' and look at 574, 854, 858 and especially 860, 861 and 862.
Most of the above have only a slightly down turned shank that you might be able to get away with on those low heeled Justin work boots. (In fact, the 574 looks pretty straight shanked to me, and with the buttons being on swingers, they can probably be kept off the floor!).
There's another important side to the spur equation, and that's the straps. I prefer very wide visalia pull though ones made by JM Capriola, (with solid silver buckles and conchos that I find and supply to them). They are two layers thick (smooth-lined), and no rough metal touches the top of my boots (important if you don't want to rub holes in your boots!). They'll make a size called "Buckaroos", which I believe is even bigger than the men's listed (call them). The wide strap helps keep the spur in place on my boot, and the wide surface distributes the weight of the spur over a larger area, making them more comfortable ( at least to me!) to wear.
I'm not a big fan of chains, but have used leather under heel straps for some of my Californio style spurs, as they tend to be lighter weight than the Texas or Northern Plains styles, and can bounce a bit more on the boot when riding or walking. (I don't like my spurs real snug on my boots; bothers my feet after awhile.)
Hope all this helps!