While it is no longer sold on modern digital storefronts like Steam, you can still access it through the following methods:
For mobile-style Monopoly games on your PC, you can use emulators like BlueStacks . Key Game Features Monopoly 3 (2002) : Infogrames - Internet Archive
Pre-owned CD-ROMs are frequently available on eBay for around $7.00 to $14.00, often bundled with other classics like Scrabble.