I am having a pole barn built here soon. I will eventually build a house next to it, for my power I'm going to have a meter on the barn and then split off to the house whenever it gets built. I'm told I need to get a 400 amp meter base. I'm also told these are hard to find by a local supply store. Can anyone point me in the right direction on where to find one? Im in Madison County, but will travel a couple hours if necessary.

Who is your power company? Normally they provide the meter base at no charge. Provide, not install. At least I know Alabama Power does.

Nah, they’re not hard to find. Lowes has them. Supply house is probably cheaper.

Amazon has one. But I would check with Mayer electric.

Huntsville utilities does not supply meter bases. But the meter base mfg you use has to be approved by them. 256- 535-1200 automated and push a lot of buttons.
Meter shop guys in this office should have a list 256 535-1314. 256-652-8492. As said above Mayer Electric supply AllPhase Electric supply. In-line Electric supply All 3 located in Huntsville and all 3 will know what HU has approved.

Inline

Inline said it'll be a year before they have any.

I don’t know all the details of what you’re planning but I would suspect it would be more economical to build a 200 service for that barn and when you build the house put a 320 meterbase with a 200a breaker to the house and feed the barn with a 100a. A straight up 400a is gonna be expensive not to mention the 200a feeder. It’s been 15yrs since I’ve done residential so some things could be a little different now.