Update: I had problems installing the bundle from nordenx's Baybayin Modern Fonts in Mojave, but found out that using its keylayout file works just fine. I'm updating the one in this repo with a copy of the keylayout from that bundle, for those who may be running into problems using the said bundle and stumble upon this repo. All credit for the layout goes to Nordenx.
Here's a layout for the Tagalog (Baybayin, also known incorrectly as Alibata) keyboard. Extract and move the two files to ~/Library/Keyboard Layouts/, then go to System Preferences/Keyboardi/Input Sources, click the +, select Others, select Tagalog, and click Add.
I tried to follow Paul Morrow's font convention as closely as possible, but I kept the punctuation marks and digits and moved the Spanish kudlit/virama consonants under Alt/Option (you can still hit Alt-= to get the virama separately).
Has Ra as U+170D (per Paul Morrow fonts) and Shift-Ra as U+172D (per current Baybayin Modern Fonts by Nordenx). Alt-, maps to the single vertical bar, and Alt-. to the double bar. Default X maps to k+s. Function keys and Option commands (e.g. Copy, Paste) should work.
Please use Ukelele to view/edit the keyboard layout.
Download here. Enjoy!