I bought a broom stick and 4 clamping collars (total weight is ~1lb), as well as the 10kg bar that Ray recommended.
That said, the broomstick is far from ideal. There are no spinning sleeves with the broomstick, and no matching collars. The collars I mentioned are affixed to the broomstick and have an ID to match it and an OD slightly smaller than the hole in olympic plates. This allows me to slip a plate between the collars, but it won't slide off. They will rattle around, and there is a small risk of them rattling over the collars.
The broomstick is also not as strong as a steel bar. Depending on what you purchase you may notice significant flex. Mine is able to (currently) accommodate 10lbs plates on either side.
Other weaknesses are a lack of knurling and rings. I supposed I could draw those on for indexes; maybe this weekend.