1kg of lead is like 90mL. I just measured my quite svelte TV remote at 22cm x 2cm x 5cm = 220mL. I'm sure you could easily fit 1.5 kilos of lead in there, and with a slightly thicker "A/V receiver" style remote we could easily make that 3-4kg
Unfortunately the venn diagram between "people who want a heavy remote for physical fitness reasons" and "people who will absolutely lose their minds when they find out it has lead in it no matter how safely you have encapsulated it" is pretty close to a circle.
