I tried those bike/handlebar sweat covers and while it may look like it works, its when you stand up on the pedals it starts to chafe the inside of your legs. Also depending on your fan placement, sweat tends to drip in other locations like behind you, on the trainer, BB/crank, etc. Those specific handlebar/bike covers are pricey at best and not movable or adjustable as I would prefer.
If you have a front or side table with your tablet/computer and with the fan(s) placed correctly, you should be able to keep cool and most sweat off the bike with a smaller gym-size towel, or better yet, I found a golf towel perfect for this. Yes I said golf! 
The center slit goes over the stem area and when I anticipate on standing on the pedals, I move the back of the towel up a bit on the top tube. The top or front of the towel is draped over the front wheel/riser to prevent sweat from hitting those areas.
Here’s the link to the golf towel which I think works perfectly…
One last note in addition to the said towel above, having a headband plus wrist band(s) helps to prevent sweat going on the handlebar and front areas.