3700X looks available everywhere.
MemoryExpress (major retailer/etailer in Canada):
https://www.memoryexpress.com/Products/MX77404
In stock and in 2nd position behind the 3600 in terms of sales - so that means their rate of sale for both these is higher than
any Intel CPU at the moment. Demand is high and stock is good on those two parts.
The 3900X is a different story -- when it launched it held the number one spot (same site, sorted by sales) for a couple weeks - that means they were selling more of this than the 3600 until it went out of stock. That means demand for this was higher than the 3600 - which we know has very high demand - so I think the demand for the 3900x is
very high. Higher than people might be thinking ...
I asked in store at Memory Express about the 3900X being out of stock and the guy said that if I want one, just place an order. He said they are coming in steadily but just not as fast as there is demand. I can see that on their website the 3900X it is right next to the 9600k in order of sales - so they are at least getting enough coming in to sell at the same rate as the demand is for the 9600k.
So in summary:
-seems to be no issues on the 3700X supply
-3900x seems to have very high demand and current sales at Memory Express show it on par with 9600k - which means stock is obviously coming in regularly, and considering the 3900x was the top selling CPU in the first few weeks after launch, before the shortage, means demand for this CPU is actually very high.
I personally am just waiting to see if there will be a 3900 non X part coming this fall, and I'll be getting myself one of those two depending on how that scenario pans out.