Based on the traditional typeface used for Irish and Scottish Gaelic, prior to 20th century reforms. I'm don't know whether this was also traditionally used for Manx, as Manx has a different written tradition based on English and Welsh orthography.

Anyway, this alphabet includes the letters and letter forms traditionally used in Gaelic:
A Á B Ḃ C Ċ D Ḋ E É F Ḟ G Ġ H I Í L M Ṁ N O Ó P Ṗ R S Ṡ T Ṫ U Ú
a á b ḃ c ċ d ḋ e é f ḟ g ġ h i í l m ṁ n o ó p ṗ r ſ ẛ t ṫ u ú

When Gaelic orthography switched over to Antiqua typefaces in the 20th century, the dotted consonants were changed: the dot was removed, and replaced with a following H, becoming BH CH DH FH GH MH PH SH TH. Lowercase ſ ẛ were replaced with s sh respectively.

Gaelic type is still used for decorative purposes, though modern typefaces are standard for formal printing. It is also used decoratively in Ireland and Scotland for English, and I filled the bottom row here with the additional letters absent from traditional Gaelic but used in English: J K Q V W X Y Z.

(UPDATE March 8: I made an 8x8px fixed-width version, but without diacritics, it's not really suitable for Gaelic language script, but works well for English.)

BACKGROUND: I used to have a much more active hobby of designing bitmap fonts. Little (usually 8x8px monospace) fonts designed for use in older 8-bit and sometimes 16-bit video games. It was kinda fun to hack ROMs to change the text fonts. Later, when Final Fantasy VI font became readily editable in 11px high proportional typeface, I started designing proportional fonts too. Nearly all my designs are revised in subtle ways over the years.