This all depends on your definition of "borrowing".
Really, here is what you can use:
In C Major:
Any chords from C Major.
Any chords from Cm (Cm, Do, Eb, Fm, Gm*, Ab, Ao*, Bb, Bo7)
* are unusual and considered rare but possible.
Also, all the 7th chord versions of these minor key chords are possible.
Any chords from any SECONDARY Key for the following chords:
ii, iii, IV, V, and vi
You can use ("borrow" if you want to call it that) the Dominant or Secondary Leading Tone Chord from any Key which can use one of the Major or Minor triads in a key as a tonic - for example, you can use D7 as the V7 of G, or V7/V in the key of C.
We don't normally call this "borrowing" though.
It is also possible to use chord progressions beyond just the dominant in "secondary progressions" (usually no more than 3 total chords outside the key but the V and one additional secondary chord is comparatively rare).
Any mode mixture chords from secondary keys are also possible.
For example, if in the key of C, you could use F#o7 which is the viio7 of V (viio7/V) - you're "borrowing" the chord from the Parallel Minor of the V chord (F#o7 comes from G MINOR, it would be F#%7 in G Major).
Some of these last two situations will be duplicates of what is already in the primary major and its parallel so usually we just see them as originating there.
There are some chords that don't really "come from other places" other than having been used and are thus considered "part of the system" though some theorists see these as alterations of other chords rather than chords in their own right, still:
Neapolitan Sixth (rarely in root position, rarely a minor chord, but happens)
Augmented Triads (many arise from voice-leading, but some are stand alone chords)
Augmented Sixth family of chords (+6, Ger, It, Fr, Swiss, non-categorized, etc.)
All these chord forms may be considered "native" to the tonal system.
However, the principle of borrowing from a parallel mode (major or minor) could be and has been extended to borrowing from OTHER parallel modes (Dorian, Phrygian, etc.).
In a sense, we could say the Neapolitan is like what would happen with a "Phrygian" borrowing.
Primary Major Key Chords:
C - dm - em - F - G - Am - Bo and their 7ths
Chords to borrow from minor:
Cm - Do - Eb - Fm - Gm - Ab - Ao - Bb - Bo7 and their 7th forms
Secondary chords (to C Major):
A(7) - B(7) - C7 - D(7) - E(7)
C#o(7) - D#o(7) - Eo(7) - F#o(7) - G#o(7)
Note: Major Triads may take either the fully or half diminished 7th chord, while minor chords take the fully diminished as the preparatory chord.
Db
This leaves relatively few chords not part of the system:
Dbm (minor neapolitan - pretty rare)
Ebm
F#
F#m
Abm
Bbm
These would be considered outside the traditional borrowing/secondary level.
When these chords are used, they tend to just be seen as chromatic chords or "color" chords - choices made for their sound rather than any functional purpose.
The real question becomes, if you're writing key-based music, how many out of key chords can you use, and in which order, before the key becomes obscured or supplanted by a new key center. That totally depends on the musical context.