אורח חיים תפ״בOrach Chayim 482

Se’if 1א׳

מִי שֶׁאֵין לוֹ מַצָּה מְשֻׁמֶּרֶת אֶלָּא כַּזַּיִת, מְבָרֵךְ עַל אֲכִילַת מָרוֹר וְאוֹכֵל, וּכְשֶׁגּוֹמֵר סְעוּדָתוֹ מִמַּצָּה שֶׁאֵינָהּ מְשֻׁמֶּרֶת, מְבָרֵךְ עַל אֲכִילַת מַצָּה וְאוֹכֵל אוֹתוֹ כַּזַּיִת, וְאֵינוֹ טוֹעֵם אַחֲרָיו כְּלוּם. הַגָּה: וּמִי שֶׁאֵין לוֹ ב' הַלֵּילוֹת רַק ג' מַצּוֹת, יְבָרֵךְ לַיִל רִאשׁוֹן הַמּוֹצִיא וְעַל אֲכִילַת מַצָּה וְכֵן הַכְּרִיכָה הַכֹּל מִן הַפְּרוּסָה, וּשְׁתֵּי הַשְּׁלֵמוֹת לְלֵיל ב'. (אַבּוּדַרְהַם בְּשֵׁם אִבְּן יַרְחִי).

The law of one who does not have protected matzah. Containing 1 paragraph: One who only has a olive-size portion of matza recites the blessing of, "about eating bitter herbs," and eats [them]. And when he finishes his meal with matza that was not protected, he recites the blessing, "about eating matza," eats that kazayit and does not eat anything after it. Rema: And one who only has three matzot for the [first] two nights should recite on the first night, "about eating matza" and "who brings forth (ha-motzi) - and likewise with the sandwich (of matza and bitter herbs) - all upon the [first] piece; and the two matzot are [held] for the second night. (Abudarham in the name of Ibn Yarchi)