I actually have an onscreen keyboard that has these layouts. Here you can find a bunch of layouts, the one called "Special" has Greek, and as many math symbols as I could stuff in, using shift, ctrl, and combinations.
∩∈⊂⊆∼≃≅≈≊× = ∃∄ℯℜ √∐ℹℴ℘∣∥≡ ∀⅀∂ℱℏℌ∫∮ℓ°∞ ℤ∠∁∇ℬℕℳ<> ≌≐≝⋍ ℚ ℰℛ∜ ℑ∅ℿ ℵℋ∭∰∱∲ ⊕⊗⊢⊣⊤⊥⊨⊩⊬ ∪∉⊄⊈≁≄≇≉≉≠ ℇ∛ ℐ∅ℙ∤∤∦≢ ∆ℾℍ∬∯ℒ∙∝ ≥≰≱≮≯
Can use it on the web.
