Q:

Do any other scriptures mention Brahma Tirtha, bathing where non-Brahmins become Brahmins? 

Mahabharat, Vana parva, tirtha-yatra parva https://www.wisdomlib.org/hinduism/book/the-mahabharata-third-book/d/doc7362.html.  Says:

One should next proceed to the excellent tirtha of Brahma.  Bathing there, a person, of the (three) inferior orders, obtaineth the status of a Brahmana, and if one be a Brahmana, his soul being purified from every sin, he attaineth to the highest state. 

Do any other scriptures mention this particular property of brahma tirtha?  

A:

Yes. 
The property of Brahma tirtha : bestowing Brahman-hood after a holy bath has been mentioned in other scriptures such as Narada Purana. 
In a conversation between Vasu and Mohini, Vasu tells about that property of Brahma tirtha

By taking a holy dip in the Brahma Tirtha a man obtains Brahmana-hood. 
This is the greatest spot of Brahma.  By going there none comes to
grief. 
[102, 65: Pilgrimage to Kuruksetra, Uttarabhaga, Narada Purana]

