You do get crushes of different sizes - not so much age-related I don't think, more to do with breed or even just the manufacturer's specifications. Unfortunately you can't take your cows to the shop and try crushes on
Though I have to say they are a very useful investment, and not just for when the vet comes. They make everything easier if you need to do checks, give medicines, drenches, TB testing etc, and if you can lift their feet you have lots of worries out of your mind too.
I am sure you can buy second hand crushes, and also that there may be grants to buy handling facilities. Our practice is writing letters for many clients to help them getting these grants and I think there's one big deadline soon - best ask if your vets know anything about it and if they do, apply for one of those.