So you have spent a lot of money on your diy quadcopter(or any multirotor) and refuse to give any more, but you still need a propeller balancer. Balanced propeller is very if not the most important thing for multirotors.
Guess what, you can make your own, from old computer components.
If you happend to work in ICT company, there is always a lot of that stuff around. Besides broken hardware, some tools may also come handy. Let's begin with stuff you are going to need.
Step 1: First things first
If you are lazy and don't care about 20 bucks, go and buy propeler balancer. Go for a booze right away.
Step 2: Stuff and tools
1. Piece of wood,
2. Set of screw thingies,
3. Drilling machine,
5. Angle grinder,
6. Broken DVD writter,
7. 4x Hard disc drive,
8. Rack server,
10. Ruler and
12. 2-8x Pen
Step 3: Disassembling hard disk drive - harvest magnets
Disassamble hard disk drive with appropriate screwdriver. Make sure you have made backup before. If you are stuck with some plastic hooks, take hammer and brake them. Repeat as many times necessary. Don't worry about hammer and you can't overdoit smashing hard drive. Now if magnet is free to take out, take another hard disk and repeat this step 3 more times.
Now you should have 4 magnets. If you have less, you don't know how to count or you dissasambled some SSD or whatever.
Step 4: Disassembling hard disk drive - harvest metal axle
Use screwdriver to unscrew all screws. Now, it won't allow you to open it just like that. Help yourself with hammer, convince him. Eventualy all vital electronic parts will move away in several dozen pieces. Take out shorter axle and throw away smashed DVD writer into garbage(recycle!). Or you can intall into colleagues PC. Either way is ok.
Step 5: Rack server - harvest hdd case
Download manual for your rack server and find a way which one of 2 possible plastic handles enables taking out hdd case. After that, unscrew 4 screws or 5 or 6, depends on the case. All you need from this are two metal side thingies. Rest of the case you can put back into rack server. Then you can practice hammering on server.