You will need:

• Screws and nuts from your old Anet A8 filament holder (or superglue).
• 8 608 bearings (get the cheapest ones for this, it's not a fidget spinner).
• 2 prints of parts 1, 2, and 3, and 4 prints of part 4.

Step 1:
Print four of "Holder_Part_4_X4" and put two 608 bearings in each of them.

Step 2:
Print two of "Holder_Part_3_X2" and slide two bearing-tracks on each of them.

Step 3:
Print two of "Holder_Part_1_X2" and "Holder_Part_2_X2". (If you already have an Anet filament holder, you can use some of those parts and save filament). Put everything together and use the screws from the old filament holder to hold it all together. If you don't have screws and nuts, you can use some superglue instead. I recycled pieces from the old filament holder instead of printing part 1 and have not printed the file, so comment if there is something wrong with it.

Step 4:
This design allows you to adjust the width of the tracks to fit your type of filament. You can slide the tracks to where you want them and superglue them to the rods if you want (I have not actually done this because my rolls of filament are different widths).

Update: I added another version of part 2, because I noticed my Anet would pull the roll off when it was almost out of filament. The new version puts the bars apart 30mm more than the original. I have not printed it yet, but I would recommend it.