can you get your hands on just the Eisbaer pump block at least? that opens the doors up a lot more.
otherwise, you can go the apogee Drive 2 (also hard to find though) and would require 2 slots only layout on the T1, and still probably be tight on the fitment.
Extreme performance Integrated Pump and CPU Waterblock
www.swiftech.com
W360, creator of the T1 is also working on a pump block combo, not sure when he will be taking orders on that one though.
2020-09-15 : revision 9 Update 2020-03-03 : Performance tested and it sucks ?, OPTIMIZATION NEXT! From left to right: 1. DDC, ≈ 6.5 L/M or 390 L/H 2. DDC + IceManCooler Top, ≈ 9 L/M or 540 L/H 3. P5 (same as EK SPC), ≈ 4.5 L/M or 270 L/H 4. P5 + IceManCooler Top, ≈ 5 L/M or 300 L/H...
smallformfactor.net
your other option is a 120mm aio, there is a fair few of them that fit the T1, but i get the feeling you are after a full loop with GPU.
At that point, you are more or less looking at the custom loop, I would checkout
@fabio's build log for some inspiration here
And again, here we are!! After 1 year and a half from my 2nd build (BTW, CHECK IT HERE if you didn't) I've moved part of it with new addition in a smaller case: THE FormD T1 !! This case is a small CNCed Aluminum jewel! I am so happy to got the possibility to be in the test shipping phase...
smallformfactor.net
if you are keen on modding an AIO, you can do this, it will void the warranty, and it's iffy on the pump power for a lot of them though, but it can be done, plenty of people have done this all over the internet, here is essentially the top two results from google in that regard for you, I personally wouldn't go this path though, could try the trading section on this forum with a WTB add, or pay the extreme shipping chargers from AC for the Eisbaer.
Edit: title updated. Scroll down! My brother has a GTX 970 and a Corsair H100i. He liked my watercooled GPU, so he bought one of Corsair's brackets to mount their AIO coolers onto graphics cards. Problem is, the hoses aren't really long enough to go anywhere he wants to place the radiator in...
hardforum.com
Others may have something else to offer, that's my two cents anyway.