Generating unimodular matrices (determinant = 1 or 1)

Maple has a deprecated function linalg[randmatrix] which has an option to make the matrix unimodular. The function generates an upper triangular matrix with all the diagonal elements equal to 1 (so the determinant is always equal to 1), and other nonzero elements randomized.
To create an equivalent matrix without using the deprecated function, you can generate a random upper triangular matrix using LinearAlgebra[RandomMatrix] and then manually set all diagonal elements to 1. Below is an example of a function that produces a 3x3 unimodular matrix.
$RandomUnimod3=maple(" proc() U:=LinearAlgebra[RandomMatrix](3,3,generator=rand(4..4),shape=triangular[upper]): for i from 1 to 3 do U[i,i]:=1: end do: U end proc: ");

This can be generalized so the procedure takes the size, random generator and whether to produce an upper or lower triangular matrix as arguments.
genUniModular := proc(size, {gen := rand(10), type := upper}) local i, U:=LinearAlgebra[RandomMatrix](size,size,generator=gen,shape=triangular[type]): for i from 1 to size do U[i,i]:=1:end do: return U: end proc:
The only required argument is the size of the matrix, the others are optional.
Usage:
genUniModular(4, gen = rand(10..10), type = lower)
to generate a 4x4 lower triangular unimodular matrix with nondiagonal elements between 10 and 10