Welcome to the way it will be for sometime to come. All industries are suffering similar problems with supplies. Mopar couldn't complete cars for weeks because of short supply of computer parts. Ford and GM closing plants because of parts shortages. It is not the fault of the sellers, it is on the parts importers and manufacturers that the problems start with. And not really a (fault). They are in the business to make money nad you don't make money if you don't have something to sell.
Look at the cost of lumber lately ?
Believe me they want to sell you as much product as they can but they are in the same boat as the buyer with getting product in stock to ship.
The end user generally knows nothing about raw materials cost/availability, production schedules ( Parts are usually made in batches) lead times, back orders AND People who are available for working.
Supply chain/ just in time parts deliveries. Raw materials, to shipping to the manufacturer for production, people to run the plant, shipping from the plant to the jobbers/warehouses. Filling back orders/warranty replacements and on. Think about what has to happen to get food items.
Plant it, grow it, hope the weather is good, pick it, process it, ship to sellers warehouses, ship tp stores, put out for sale. Any interuption in any one part of this chain and the end result is the end buyer(consumer) has nothing to buy.
REGULATIONS
All you can do is keep being the squeaky wheel, Call, leave messages, emails, heck even snail mail and know that the seller wants to send you your stuff because he is counting on you to buy more stuff. That is what business is all about.
Good luck with your project and make sure you Vote !!!