Actually, the correct belt is the 44783AG Hoover belt. It is very slightly thinner than the 49258AG convertible belt and a little more easily stretchable. They are not easily found these days but are still available from some online suppliers , specifically Hescoinc.com for $1.19 each plus shipping. Enter part no. H-44783AG.
Yes you can use a Eureka RD belt but it is just too big and will quickly begin to slip.