Your best bet would be to order the 1000 dose vial, and use it within an hour to vaccinate your chicks the first day at home. You have to get a cooler and ice packs which increase the cost, but it is not that expensive. Be sure to keep the chicks isolated from any area that may exppose them to Mareks for 2-3 weeks until they develop full immunity. Here are some links on giving the vaccine, as well as where to buy it: https://countrysidenetwork.com/dail...inister-the-mareks-vaccine-to-poultry-chicks/
Just fyi. I was going to do this myself but couldn't.
I made up the vaccine, had my tiny insulin needles at the ready, my cotton balls and alcohol to clean them and...
I was so afraid to hurt them. Day old chicks are not like puppies. They do not have extra skin behind their necks. I honestly have no idea how anyone does it. Props to them.
I did lose one chick to mareks. It was very sad! But I just couldn't do the vaccination. They are so squirmy and delicate. And that needle is sharp and you're supposed to stick it under their skin but seriously there is no extra skin there.
In my opinion, if you are broody rearing your chicks then you are probably wasting your time and money on getting the vaccine. If there is any latent Marek's virus in your flock, the chicks will be exposed to it via the broody prior to the vaccine having time to take effect.
There are not places/clinics that you can take them to get vaccinated, so you would have to do it yourself at home and as @WhiteWyan says, it is not easy if you have never done it before. There are also issues with the vaccine that is available because it is leaky and may not protect them from all strains.
The chicks really need to be kept in isolation from the time of hatch until the vaccine is effective (not sure offhand, something like 2 weeks?). Since they'll be hatching under a broody, there's really no point. They'll be exposed immediately.
It's extremely common actually, it's spread by wild birds if I'm not mistaken. I've been lucky so far inasmuch as I have never seen anything that resembles it in my flock. Now, that doesn't mean none of my birds are carriers, they very well may be carrying it and have such a good tolerance that they never have an episode. Hard telling without testing. My last chicks came vaccinated, but the birds I had already weren't.