You are ambitious!
You say you "have 15 vintage and antique cameras" but I read that as you "have 15 very time consuming and nuanced projects on your hands!"
I have been shooting with vintage cameras for nearly two decades and every camera has its own story and challenges to bring back to life.
First step is to identify what film each camera takes and if you can still get it or not! If you've got something like a Kodak disc camera, you're never going to be able to use it again anyway because film hasn't been and will likely never be made for that camera again. Your best bets are 35mm, 120 and large format cameras. Some other formats are also available but are less common and more costly so you really have to weigh your desire to shoot them with the practical expense.
But hold up! It's not worth buying film for broken cameras so before buying, verify that obvious functions actually work before you go buying film and flash bulbs. If you can't get a shutter to fire, it may not be worth buying film until you've carefully red the users manual for the camera and/or had the camera CLA'd (Cleaned Lubed and Adjusted) by a professional repair tech for anywhere between about $60 and $200.
NEXT step is to buy your film and I recommend the following shops from which to purchase film:
Work out what film formats and ISO's and brands you want, how much they cost per roll and how much the shipping will be to determine who you want to buy from.
After you actually USE the camera with film, you may still find functional problems that need to be addressed. See why I say that these are 15 separate projects?!
Okay, and your next question was flash bulbs. Look, bottom line is, pretty much everyone in the world shoots digital to some degree. Of those people, very few people shoot film And of THOSE very few people even fewer people use flash bulbs.
Flash bulbs litter eBay for pennies on the dollar. They are very cheap because they lurk in everyone over 30's closets and are worth next to nothing because they aren't be used much.
Why? Because GOOD cameras can use electronic flashes which are more accurate and can be used more than once! Many times more than once. And also, modern films are more light sensitive so you don't often time, even need a flash.
There are some GOOD flash units that require flash bulbs but they are very old and in most cases can be replaced with an electronic flash. MOST vintage cameras out there that use flash bulbs are fairly worthless consumer grade cameras that more or less rank as toy cameras. Not all, but most.
You certainly don't NEED to use flash bulbs to operate most cameras that are worth operating. So I am not sure what you have or why you would be looking for these but I'd recommend concentrating on the above tasks first.
If you really want to use flash bulbs, the ONLY thing to do is to find out what model(s) you need and buy them off eBay. Reputable used camera shops don't sell them. Period.
So look, I hope that I've helped you with your projects. You are going to need a lot more though. So please be kind enough to choose a best answer and go ahead and ask more specific questions about each camera as you riffle through and play with them. Using vintage cameras is a fun challenge. Emphasis on the challenge!