Gen. Jack Keane has suggested that the US obtain funding for the Ukrainians by 1) seizing the $300B in Russian assets that are frozen in western banks, 2) loan goods to Ukraine on lend lease basis, where the Ukrainian Government is obligated to repay the funds to the US with an interest rate, or 3) use existing Ukrainian assets, such as rare earth minerals, to secure payment for equipment.
I would prefer the first, where Russia pays for its own defeat, using the second and third options as fall-back positions.
Here is an interview with Jack. They were discussing a Washington Post article he co-wrote with Marc Theissen.