A solution was inspired by this answer to a related question, here:
How to emulate LPAD/RPAD with SQLite
I wanted to share this on Stack Overflow, as this may be useful to other SQLite users. The solution goes like this:
-- X = string
-- Y = number of repetitions
replace(substr(quote(zeroblob((Y + 1) / 2)), 3, Y), '0', X)
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