Find out which channel is fairly vacant at your field. Send the TX to Horizon or Radio South to have it changed to the new channel and tuned for peak performance. About $50.

Swap crystals in the JR receiver so it is on the new channel.
Since Parkzone is a Horizon 'house brand' it is possible that it is compatible with your JR transmitter. Call Horizon tech support and ask. If it is, you only have one receiver to buy (for the Tucano)

Hitec has an auto shift 8 channel receiver, available from tower for $39.99
http://www3.towerhobbies.com/cgi-bin...&I=LXKYK3&P=SM
Crystal $7.59
http://www3.towerhobbies.com/cgi-bin...I=LXN503**&P=M


I almost forgot about this receiver option. It is auto shift. It is tiny but it is a full range receiver that can be used in big models
Castle Creations Berg Microstamp 4L 4Ch Micro Rx FM $29.99
http://www3.towerhobbies.com/cgi-bin...&I=LXLBY8&P=ML
Crystal $6.79
http://www3.towerhobbies.com/cgi-bin...I=LXMAH4**&P=M

The 7 channel version is $51.99 plus 6.79 for the crystal
http://www3.towerhobbies.com/cgi-bin...?&I=LXRJM0&P=M