Quantity   Component name
1 × ESP-01 ESP8266 WiFi Module $4
1 × MT700 Barcode scanner engine (marson) $38 (MOQ!)
1 × 2.2" 128x128 GLCD (ST7541 Controller from www.buydisplay.com) $7
1 × PIC32MX250 44 pin processor 128K Flash / 32K Ram ($2.70 microchipdirect.com)
1 × RC522 RFID reader module (Approx $3)
1 × 4 x 4 membrane keypad matrix ( custom made for about $20 each) Note you can also implement using discrete buttons
1 × SMT capacitors/resistors/connectors/8Mhz XTAL (no more than $5 the lot) (these may change a little so best to refer to circuit for now until stable)
1 × MCP1725 500mA LDO $0.40 (Microchip Direct)
1 × Modified ABS Enclosure 135mm x 70mm x 24mm Camden Boss 2950-39B (http://camdenboss.com/enclosures/handheld-enclosures/ir-pocket- The main size constraint is the kbd and lcd screen plus the height of the barcode scanner on the board a tigher configuration than mine should be possible though you should constrain any size so it is suitable for handheld use. the above case is more commecrcially available than the one I got from china, however the PCB Holes will have to be moved back a little as the mouting screws are 58mm apart not 56mm
1 × 3.3V piezo buzzer $1
1 × RFID coil approx 500uH about $0.50 or wind yourself
1 × LiPo 3.7V 1200mAH battery (type depends upon your enclosure) or bigger/cheaper/whatever fits your case
1 × TP4057 LiPo charger ($0.25) ebay/aliexpress