Hi @Mark,
You describe this as an urgent situation, and I genuinely do not want to make things harder on you here, so for now I have uploaded the 3.9.0 files for Filter Bar here → https://cloudup.com/cm6Mo4EeaAp (only The Events Calendar and some other add-ons had 3.9.1—Filter Bar and others only went to 3.9.0, but it’s all the same 3.9.x release family!)
I would recommend pestering the developer of that third-party software to update their code to work with our most recent stuff—there are some serious security weaknesses when using old software like this, not to mention all of the code/performance/feature improvements etc.
We also cannot support the old versions, so if you install this 3.9.x software and have issues/conflicts on your site, step 1 of any support interactions would be “Update to most recent…”
I’m sure you know most of these things, @Mark, I just wanted to clarify them! Check out the link above for Filter Bar 3.9 and download the zip for it.
Best of luck with your project,
George