And here's a decent backup:
https://church.founders.org/
They can't vouch for every church that submits its name to this list, but it's managed by Tom Ascol, one of the leaders of the Reformed wing of the SBC, so most churches that volunteer for this map probably know they're making a statement in doing so.
Just a caution -- these lists are good but they are not perfect and need to be used with caution.
In our area, there are four churches which appear on various "Reformed Baptist" lists.
One is a solid Reformed Baptist church, mostly homeschoolers -- Briarwood Baptist on Highway 28 between Dixon and St. Robert. I've known the church for over twenty years and watched its former pastor, now deceased, as he took the church from being a typical conservative SBC and brought it to a Reformed position. The men are brothers and while I don't agree with them on everything, and obviously I disagree on baptism, I have referred Reformed people there and will continue to do so. They are led by two lay ruling elders who have shared the preaching duties after their former pastor, now deceased, lost his vision and could no longer do so.
Another, the Assignment Community Reformed Church off I-44 near the Pulaski/Laclede county line, was pastored by a godly Black man who was originally ordained as a charismatic pastor, became Reformed, and over time lost most of his members. The church closed quite some time ago when the building they were renting was discovered to have a serious black mold infestation and the owners decided that for liability reasons they couldn't have people continue to meet there. Their former pastor is a godly man who has significant medical issues in his family, which are not secret and he has made them public. He would appreciate prayer, but his former church no longer meets and needs to be deleted from that list.
In doing some additional research, I discovered today two other area churches that appear on "Reformed Baptist" lists, one in our county and one close to it. I'm not going to name the churches or the lists. I personally know one of the churches and I was not aware until today that anybody in the church considers themselves to be Reformed. I am all but certain this is an error. The other church is a traditional Baptist church that may have recently moved in a Reformed direction, but if it were known for being Reformed, I am all but certain I would know. I plan to privately speak with leaders in the first church that I know, and reach out through mutual friends in the second church, to see if this is a mistake or if the churches have recently made major changes in their doctrinal positions.
I'm not trying to attack or criticize but rather to remind people of the need for caution. Almost by definition due to the polity involved, "Reformed Baptist" is a pretty broad term. It's not like the list of NAPARC churches for which there is a vetting process and accountability. That's not perfect either -- one PCA congregation may look very different from another PCA, and there are solid local churches outside NAPARC in denominations like the EPC and CRC -- but people need to do their research and check churches out.
I speak from personal experience here, having moved several times for employment and found out after I moved that things were not what they appeared to be in the local church. That was (mostly) before the modern internet and many more resources are available today to check out a church than used to be the case.
maps.app.goo.gl
reformedbaptistchurches.com
fellowshipgc.com
