Current limiters using transistors and diodes
The original circuit is a "low-side" current sense. The first variant is a voltage source with a high-side current sense. The second variant is the same but is now adjustable (tweak trip current). The third variant replaces the two diodes with a transistor to make it a little more precise. All these circuits are not going to be very precise as the Vbe junction of any transistor is sloppy and changes a lot of temperature. The low side vs high side just depends on your application (maybe you don't have access to the high-side).

The three transistor version is going to be the most precise and give you adjustments to trim some error and tune the current trip level.