-garbha as a name suffix seems common enough among authors of Tantric texts, or from Tantra-influenced milieux. A quick search through
Genesis and Development of Tantrism, ed. Shingo Einoo, (Kyoto, 2009) yields many examples, including a Nārāyaṇagarbha.
For the graphic similarities cited, these samples are from the Ojha publication Ashok cites:
<Screen Shot 2014-02-08 at 8.01.36 PM.png>
These are 16th c. Sharada examples from Plate XXXI of the same (the second, /bha/, is not necessarily closed)
<Screen Shot 2014-02-08 at 7.59.42 PM.png>
<Screen Shot 2014-02-08 at 8.00.00 PM.png>
Compare also these, from p. 62 (on Śāradā) of Hemarāj Śākya's _Nepāla Lipi-Prakāśa_:
<Screen Shot 2014-02-08 at 8.20.34 PM.png>
Certainly close enough to me mistaken given natural variability.
Also, consider the ta and bha rows in the attached chart, especially for the scripts listed as Vartula, Nepali, and Nandinagari.