Q: Is there anything that I can use to temporarily grease my CV boot for a couple days until I can buy more grease?

Hello. I am sorry to hear of your situation with the CV joint and boot on your 1991 Metro and will try to help you now. Typically, once the boot rips, the grease inside will actually stay there for a reasonable interval, often enough time to be able to re-use the joint along with a new boot if you clean everything well. You would really have to run through a flood or a mudbath to dislodge the grease or contaminate it enough to ruin the joint "immediately" after the boot tears.

But, in your circumstance you are mentioning that you believe the joint is noisy. If the noise is coming from the joint (and not, say, a wheel bearing) I would not bother continuing to add grease because you are going to have to replace the joint anyway. If there is any noise at all from the joint now, it has failed and is not reusable no matter how much grease you add or what type. If you intend to replace the joint within say a couple weeks or so, adding grease will do essentially nothing to help the joint.

If the noise is actually "loud" and you feel that the joint is both the source and is mechanically impeding the wheel from turning you definitely should not drive the car until the axle is replaced. If the joint is noisy and, worse, is binding, you could damage the transmission and if the axle breaks apart at the joint damage the car and possibly cause a crash. So, the bottom line is if the axle is really noisy (and again you have to make sure the noise is from the joint and not a wheel bearing which is not an uncommon failure after 10 years, let alone 25 years in your case) unfortunately you just simply have to replace it. This is a common repair, and YourMechanic has Technicians who are uniquely qualified to replace your cv boot for you at the convenience of your schedule.