There's a special Agoda link that will get you to the SHA Extra Plus packages.
Google Agoda test&go and you'll find an article that should show it you.
The problem is that even if you book on Agoda you'll need to get in contact with the hotel to get the booking confirmation from them. I'd just look for some higher class hotels you find on Agoda and contact them directly or even call them for fastest service.
I booked with Grande Centre Point Terminal 21 and they sent me links to pay by credit card, though for some reason I couldn't get visa to work on either one and had to use Mastercard.
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The biggest delay right now is that after you're booked your hotel has to login to the new hotel confirmation system and enter your information there so that Thailand Pass knows the booking you submit is authentic.