Question: low-budget extended run ideas?

Hi all. I have three 2 year old hens in a modified "Wichita cabin coop" style coop and run who are used to free-ranging most days on our unfenced acre. They're locked in the secure coop each night. For the last 2 years, they've been great about staying right around the house, but the last two weeks, they've decided to venture over to the neighbor's yard now and again and while my neighbors don't mind the chickens, we both worry about their dog attacking them while over there. I've kept them cooped up in their 4'x8' run the last 3 days since I found out about their escapades, but need to find a better solution going forward. They're used to spending a day or two locked up when it's really rainy or we're away for the weekend, but they're already letting me know they want out to roam and forage.

I have a pretty limited budget at the moment and was thinking about using some t-posts and 48" plastic fencing to fence off an area around their coop so they could have more room to roam during the day. I'd still lock them in their coop each night, but I'm wondering is this is a good solution to my problem. Has anyone else done something like this? I know it doesn't provide any predator protection, but then they had very little while free-ranging either, except that they could hang out under the evergreens to hide from aerial predators etc., which they won't be able to access now. I could build them a basic little shelter for that area to huddle under when they see a hawk/eagle though. I live in a rural area with hawks, eagles, raccoons, mink, and the occasional random dog being the big chicken predators.

If this isn't a very good short-term solution (in the future I'd like to revamp my coop into a bigger one with a large run, but being on a decent slope, it's a bit tricky and budget-wise, that's a year or more away), do you guys have any ideas to give my girls more room to roam, while keeping them away from my neighbor's yard? Fencing my entire property isn't an option at the moment, as appealing as the thought is.

Thanks in advance!!