where can i find a touch sensitive light switch that can replace my current wall switch?

You can find these types of switch's at a number of locations!  One is at sourcing match where it is sold for $4.99!
specifics:

• Locator light display for easy access the Pressure Sensitive Switch in the dark
• Save on energy costs and helps extend bulb life
• Ideal Wall Switch for any room in your home
• The Touch Light Switch suitable for alleyway, veranda, washroom, carbarn, basement
• Light will be turned off in about 55-75 seconds after touch
• Only suitable for incandescent lamp, not for fluorescence lamp and energy saving lamp
• Notice: Please install by professional electrician under the instruction
• Size: 85mm*85mm*25mm
• Weight: 55g

Best Offer also carries it and it sells for $7.99 and free shipping!
specifics:

• Voltage: AC180-250V 50Hz
• Power: <= 100W
• Static power: < 0.2W
• Last time: about: 55-75 seconds

There is also a dimmer touch master that sells for $22.69!
specifics:
Touch-sensitive pad for on/off pad dimmer control. Quick touch turns on/off, touch and hold for dimming. "Remembers" previous light setting while lights are off. Easy to install. No additional wiring required. 6" prestripped wire leads for fast, easy wiri ng. Ground lead provided. Bezel fits decorator wall plate. Air gap on/off switch for servicing fixture. Wrap around heat sink dissipates heat and does not require de-rating. U.L. Listed.