No real relation other than both Monstera and Scindapsus are in the family Araceae and tribe Monstereae. They are both similar in that they start out life as shingle plants, with leaves appressed to the growing surface. Monstera dubia, however, changes leaf shape and growth habit after it climbs some up a tree. It starts developing larger perforated leaves without variegation and without the shingling habit. Scindapsus pictus is neotonous, remaining in its "juvenile" form its entire life. Another difference is Monstera is a wholly Neotropical genus while Scindapsus, Asian.
Check Ebay now and then, Brian W. occassionally has Monstera dubia for sale.
Michael M.

Wow Michael! Great response! I'll copy this and add to my notes.

More detail: Monstera Dubia