in 2019 I purchased the EVGA SuperNOVA 1600 T2 1600W 80 Plus Titanium Modular Power Supply. Are there updated EVGA cables I can purchase (12VHPWR?) for new GPUS? Or is the 12VHPWR cables only available on new PSUs with the ATX 3.0 standard?

I think you should try cablemod as they might tend to have this. Contact them directly if needed. 

Welcome to the Forums!
 
The 1600 T2 PSU is not a native ATX 3.0 power supply, so in this case we do recommend using the adapter for the 12VHPWR that is usually supplied by the manufacturer that makes the graphics card that requires this type of connection. 
 
Alternatively, if you do not wish to use an adapter, we do offer a newer ATX 3.0 power supply that are available as shown on the links below.
 
EVGA - Articles - EVGA FTW PSU
EVGA - Articles - EVGA XC PSU
 

bluewhale9
in 2019 I purchased the EVGA SuperNOVA 1600 T2 1600W 80 Plus Titanium Modular Power Supply. Are there updated EVGA cables I can purchase (12VHPWR?) for new GPUS? Or is the 12VHPWR cables only available on new PSUs with the ATX 3.0 standard?

A newer PSU will probably be your best solution as Chris has recommended. 

Quick question for ChrisB.  Is there any reason why he could not use this ??  https://www.evga.com/products/product.aspx?pn=100-NK-3000-B9   I know it says 3090 founders edition and ftw ti , are the pinouts different on those two cards compared to the rest of the 3090 series ? 

This cable does not have the 4 pin sense cables on it that are required for 4000 series.
 
As to the comments above suggesting you replace a Titanium tier PSU with a Gold rated PSU from a company that is basically defunct and only has a 3 year warranty is also insanity. If you are going to buy a new PSU there is plenty of great options. I replaced my 1200P2 with a FSP Hydro Ti which dominated the cybernetics test. If you want to keep your current PSU which will work fine then cablemod makes cables to do so
 
 
https://store.cablemod.co...-g7-g6-g5-g3-g2-p2-t2/
 
https://store.cablemod.co...in-to-dual-8-pin-60cm/
 
 

just ordered a gen 4 type 5 cable for my p2 psu