Here is an update on my search for a replacement boot for the tie rod on my Mahindra 4550
I found a pair of silicone boots that fit perfectly for a cost of $3.90 plus $5.20 shipping out of Bulgaria.
They took about a month to get here, and I've had them on the tractor for a month testing them out. So far so good. They are not as robust as the OEM boots but their working. I also beefed up the bracket on the guard that is in front of the tie rod to further protect the boot. If anyone is interested in where I purchased the boots, PM me for the info.