I bought some 18650 holders to use for charging but the plastic/metal on the holder tore up the top my 18650s casings up.
Didn't fix the holder until after it removed the top covers of 2 batteries.
Now I am tired of putting a battery into a light and seeing a nice spark from the metal touching metal touching the positive.
Or worse, having the spring cause the spark inside the light. :X
How can I fix these bare tops?
Topless Pics (as promised):
Perhaps a flattened piece of plastic cut to fit around the positive post and rewrap them?
That would work, but is there anything that doesn't require new wrap or special tools?
I had electrical tape with a malformed circle cut out on them earlier, it doesn't stay in place very well and it there is still exposed metal that shouldn't be.
FT has 18650 heatsrink wrap in a many colors.
$1.18 clear See “Available models and parts” for other colors. Blue is $0.84
You can shrink it with a lighter.
You could try clear packing tape folded over the edge. New wrap will be best tho.
Rewrapping is reeeeeeaaaaaallly simple, and really cheap (10 cents per cell, roughly).
I actually just did it this morning, but I had the original little flat plastic donut deals around the pos post. Far easier than I anticipated.
I don’t like the clear plastic though… makes them look Neked.
Came for the topless pics. Honestly, a bit disappointed. At least they are in pairs….
You don’t like naked yet you come to the topless picture thread. 
Do you prefer bigger or smaller?
We could put the call out for topless 26650s or 14500s.
Even 32650s or 10440s.
You can use heatsrink wraps, as has been suggested, and if you rush to put “something”, use the nail polish, I use it for isolating the electrical contacts, it is durable and you take it with acetone.
+1. Re-wrapping is easy, and takes about 5 minutes or less (per cell). I use my hair dryer with great results.
See this post here, on BLF.
Can I get wrap from anywhere in the US?
Last fasttech order shipped USPS and took nearly a month.
You can also use a small o-ring at the top of the host for a battery bumper. It may help prevent any further wrappers on the batteries from coming off.
Shipping doubled the cost, but that didn’t matter to me. It got here in 3 days. Ended up about 16 cents per rewrapped cell.
How do you order more than 1?
They are sold by the foot, but it says: Availability: 1 on the product page and "Products marked with *** are not available in the desired quantity or not in stock!" at checkout.
This is where I got my last 18650 shrink wrap. Although purchasing from RMM (mtnelectronics) helps support a fellow flashaholic. PM him or ask about the order in this thread. MTN Electronics: LEDs - Batteries - Lights - Chargers - Hosts - Drivers - Components - 1-Stop-US Source
Thank you for the links. I didnt realize RMM was a member here.
Fasttech says my batteries are 18mm x 69mm (D/H x L)
What size(mm) of heat wrap do I need?
29mm is as small as you want to go, most consider this size perfect. But the 31mm that I linked works great there’s a little more room to work with and does shrink down tight to the battery even at the cut ends. I did 2 batteries just a few days ago, works like a charm.
.
Edit: By the way that is flat heat shrink, measured across the tubing when flat, like in the pics a ebay.
Good thread that might help. Tutorial: Rewrapping a battery
Here's a topless pic for ya!
Ah, I bought several feet. We may have depleted his stock down to only a foot left. 
Humbrol Maskol - used to use it to waterproof the ignition on an elderly motorcycle. If it'll work at those voltages, it'll be fine with 4.2V.
Sold in model shops for masking models prior to painting.