I try to avoid MDF for fret and scroll sawing to avoid wearing a dust mask all the time while working.
It's worth visiting the US-based Ocooch Hardwoods website.
I contacted them after finding out that that they sell up to 8" wide and up to 1/2" thick hardwoods in a great variety.
Admittedly, international shipping is not exactly cheap, but then it's in $, so not that bad.
As I have so far no resawing facilities, it's time to save up for some 8" wide boards.
And finally, with the help of Google translate a visit to the online shop from the German scroll sawing magazine Feinschnitt kreativ can also find some interesting offers.
It's somehow funny, that I have all their magazines and never attempted any of the bigger projects for a lack of wood and only now had a look at their shop where you can get woods like elm, walnut, cherry, pear and others at 450 x 450 x 10 mm boards and even some veneered plywood with walnut or bamboo for example.
Maybe I should start putting some of my veneers on plywood sheets and sell them to raise money for some hardwood.