You can make your own balum very easy you can find instructions in Amateur Radio Handbook you may be able to find it online. You need some very tiny ferite donuts and enamel coated copper wire. Hardest part of making your own is getting inside of some type of case. A short piece of small diameter PVC pipe or copper tubing works. The time it takes to make a balum outweighs the cost of buying one but you know the quality of what you have and you know your homemade balums are all identical.