sirina and other power heads
This depends on how the power head gets its power. If the hose end is standard and has a two prong mini female connector as many other vacuums do, than yes, it should be possible to connect one of the universal power heads that are available. I don't have a Sirina so someone who does would need to comment on whether the electric connector is the standard one. If so, you would have several options, the Sebo power heads have an adapter available that makes them universal, Lindhaus also makes a model of their power heads with a universal pig tail cord, as does Riccar. Or you might consider getting the volt power head from Tacony, since that's also a dirty air design, it would increase the cleaning power of the Sirina quite a bit. The Wessel Werk heb160 is made in a universal version as is the EBK340. The EBK360 has a quick connect interface but you can make a cord that will make it universal. Again, the easiest nozzle to use here might be the volt.