The WiFi driver can be downloaded from here: https://github.com/lwfinger/rtl8723bu If you are compiling on the Raspberry Pi 2 or another ARM device you will need to change the SUBARCH build parameter in the Makefile to “arm”.
The Bluetooth driver is here: https://github.com/lwfinger/rtl8723au_bt/tree/troy (The Troy branch works with this module).
Before running make install it is advisable to rename or move the existing btusb.ko[.gz|.xz] module to stop it from being overwritten and, conversely, to make sure that it isn’t still used. It is usually located in /lib/modules/$(uname -r)/kernel/drivers/bluetooth
You may find that either the Bluetooth interface or the WiFi interface is blocked when you have both drivers installed. Use rfkill list and rfkill unblock to determine if either interface has been blocked and then unblock it. This should allow you to use the WiFi and Bluetooth simultaneously.