Would something like this work or is he committed to using his hands instead? Manual or automatic might be helpful for other suggestions as well.

https://www.amazon.com/Source1mobility-Accelerator-Stroke-Assist-Handicap/dp/B01AYOBL0Y/ref=sr\_1\_1\_sspa?crid=7JKZ7Y2SJSNM&dchild=1&keywords=left+leg+gas+pedal&qid=1624399798&sprefix=left+leg+gas%2Caps%2C235&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFONUlUN1FFUU9QWUcmZW5jcnlwdGVkSWQ9QTEwMjYzMjAxVEpXWUhLMUQzRkcmZW5jcnlwdGVkQWRJZD1BMDI4NDY5OTEwTzhMUjVFQlVUNVMmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl#customerReviews