Thank you for your great suggestions Flashy Mike & DavidEF!
I‘ll think about it. Has anyone of you an idea how far the Seoul Viosys Z5 UV LED can be overdriven? Is 1.5A still below the threshold of harmful current? Those UV LEDs are quite sensitive for higher currents. I‘m afraid I can‘t go lower than this. Or is there an even better UV LED with 3535 footprint?