Amazon with the Chicago Tool Company has the DeWALT 7.5" Wet/Dry Vac Replacement Filter (DXVC6910) for $20 with free shipping on $35+ or with Prime.

Measures 8.7"L x 7.5"W x 7.5"H. Compatible with DXV06P, DXV09P, DXV09PA, DXV10P, DXV10PL, DXV10S, DXV10SA, DXV10SB, DXV12P, DXV14P, DXV16P, DXV16PA, DXV16S wet/dry shop vacuums.